Nintendo details Wii U network ID system - Polygon
I couldn't access the store on my Wii U, I can't remember if I removed my Nintendo ID from the previous one. Would that cause this message to pop up? : r/wiiu
How to Add Friends on Wii U: 11 Steps (with Pictures) - wikiHow Fun
How to setup a Nintendo Network ID- 3ds, Wii U, and Nintendo Switch - YouTube
What is a Nintendo Network ID? | Wii U | Support | Nintendo
How to Find Your Nintendo Network ID - Wii U Wiki Guide - IGN
Important Steps to Bring the 3DS and Wii U Closer Together - Talking Point | Nintendo Life
Is a Nintendo Network ID necessary for each family member? : r/wiiu